[48.16] Progress with CZT Detectors for High Energy X-Ray Astronomy

CZT (Cadmium Zinc Telluride), a room-temperature
semiconductor, is a very promising detector material
for high energy X-ray astronomy. It can operate
from <10 keV to >200 keV, and give sub-keV
energy resolution and sub-mm spatial resolution.
Thus it is attractive for both focusing instruments
with small fields of view, <1^\circ, and coded
mask instruments with large fields of view,
>10^\circ. We report recent progress on CZT
detectors by the UCSD/WU collaboration. Three
detectors were used: a 25 x 25 x 1.4 mm^3
detector with orthogonal crossed strip readout using
375 micron pitch electrodes, manufactured by
Digirad, (2) a 12 x 12 x 2 mm^3 detector with
orthogonal crossed strip readout using 500 micron
pitch electrodes plus "steering electrodes" to improve
the anode charge collection, manufactured by eV
Products, and (3) a standard 12 x 12 x 2 mm^3
planar detector manufactured by eV Products. The
eV Products crossed strip detector achieved
\sim4.5 keV resolution with no tailing at 60 keV
using commercial electronics. Uniformity of spectral
response versus position and absolute accuracy of
spatial response were measured with a finely
collimated, 30 micron diameter, X-ray beam.
Inaccuracies of inferred interaction positions of a few
100 microns were often observed. The latter 2
detectors were tested on a balloon flight to
determine their energy resolution and background
with several passive shielding schemes. Model
calculations were made of charge collection and the
effects of the steering electrodes' bias and compared
with laboratory results. We also report on future
plans which include the integration of detectors, bias
networks, and readout ASICs to form the "plug-in
module" which is planned to be tested on a balloon
flight in March 1998.

The author(s) of this abstract have provided an email address for comments about the abstract: jmatteson@ucsd.edu